


Croí (Heart)

by the_heart_and_the_brain



Category: Septiplier - Fandom, jacksepticeye, markiplier - Fandom
Genre: Alpha!Mark, Alpha/Beta/Omega Dynamics, Alpha/Omega, Anal Fingering, Anal Sex, Knotting, M/M, Mating, Mating Cycles/In Heat, Omega!Jack, Rimming
Language: English
Status: Completed
Published: 2016-12-10
Updated: 2017-02-10
Packaged: 2018-09-07 16:23:23
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 5
Words: 4,579
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/8807746
Author URL: https://archiveofourown.org/users/the_heart_and_the_brain/pseuds/the_heart_and_the_brain
Summary: In his haste, Jack has failed to pack his suppressants, and now he has two weeks at Mark's house...





	1. Chapter 1

**Author's Note:**

> I've noticed there is a severe lack of A/B/O Septiplier fics so I decided I'd start to remedy that.
> 
> I love writing A/B/O so expect a few of these in the future :)
> 
> Croí = 'Heart' in Irish Gaelic

Jack grinned as he started to unpack his things, putting clothes in the empty drawers and his laptop on the desk. He was going to be staying with Mark for a couple of weeks, doing some videos together before Mark took him to see some of the sights. He had been waiting for this for months and was so happy to finally be here.

The spare room was spaceous and light, filled with the underlying scent of the Alpha – spicy, woody, warm and exotic. Jack inhaled deeply, a small thrill running through his body before he shook his head and continued to unpack.

The Irishman had been born an Omega but passed as a Beta, using products that made him smell like one whilst taking suppressants to stop his heats. None of the YouTubers or his followers knew his true sub-gender, or even questioned him. True, he had the usual Omegan characteristics, but a lot of Betas did. He was pale and slender, handsome in a way that could be described as beautiful, with big blue eyes and soft hair dyed green.

But he didn't want it, he didn't want the stigma of being an Omega, of having people assume all he was good for was to have babies and for serving an Alpha – so he hid it.

Organising his toileteries, Jack realised his suppressants weren't with the rest of his things. He emptied the bag on the floor and pushing aside Beta scented products, but found nothing.

“Oh shit...” He muttered, pulling the last items of clothing out of his bag, frantically patting the inside for the telltale bottle of pills. “Shit, shit, shit!” Dread was ice cold and heavy in his stomach as he realised that they weren't there, that they had never been there.

In his excitement, he had completely forgotten his pills...

“Fuck! Stupid stupid _stupid!_ ” He hissed at himself, running a hand through his green hair and tugging at the strands.

_Stupid biology...stupid pills...stupid Jack..._

Tears pricked at the corners of his eyes, angry at himself for being so stupid and frustrated at ever being born an Omega. He fought the urge to curl up and cry, blinking the tears away before they had a chance to spill.

Maybe it will take a few days for the hormone-blockers to leave his system? Maybe his heat will be delayed until he got home? When not on suppressants, his cycle had been erratic at best.

All he could do was hope.

* * *

Mark watched the younger man from across the table as they ate, the Alpha had noticed Jack's demenor change but he couldn't figure out what had caused it.

Was he regretting coming to visit?

The red head shook his head slightly to get rid of this thought, but as he glanced over and saw Jack picking at his food, he couldn't help but wonder.

“Hey, you okay?” The green haired man looked up, those big blue eyes holding his, and sighed.

“I'm pretty tired, probably jet lag...I might go fer a lie down.” Jack did look pale and tired. Mark nodded, smiling reasurredly.

“No problem, you go and rest up. I'll clean up down here.”

Once Jack had left the room, Mark ran a hand through his red hair and sighed. He had been wanting Jack here with him for so long, his affection for the Irishman having grown from strength to strength that now he could safely say that he loved the other man.

He knew as an Alpha there were traditionalists who believed that he should be with an Omega, but he didn't care, he wanted _Jack_...whatever sub-gender he was.

But as he heard the other man walk up the stairs, a small voice in the back of his head, the one that always played up to his insecurities and fear, told him that Jack would never love him.

And no how many times he shook his head, the voice wouldn't go away.


	2. Chapter 2

Jack lay on the bed, staring up at the ceiling, dread curling in his stomach. Just his luck, the symptoms were already starting to appear; the telltale itch under his skin, the feeling he was burning up, the slow trickle of slick between his legs.

Covering his face with his hands, the Omega groaned quietly to himself. He was no stranger to heats, the last year or so he had gotten through them with thoughts of Mark...but he didn't want this situation to ruin their friendship. He didn't want instincts to take over and for him to do something that could irreversably damage what they have

No matter how much he wanted to...

Rolling onto his side, he curled up into himself and quietly sobbed, muffling the sounds into the pillow.

God, he felt like his heart was already breaking.

That didn't stop his mind from providing images in his head of the redheaded Alpha taking care of him, pinning him down, knotting him. Jack groaned into the pillow, hips rolling as the slick feeling between his legs increased, soaking the pyjama bottoms he wore.

He had gone from idolising Mark to meeting him and them quickly becoming friends. But now...now he felt so much more for the other man, an almost constant deep seated ache to be close to the American. But he didn't want this, he didn't want hormones and instinct and biology to ruin what he had so carefully built.

He wanted Mark to love him for who he was, not _what_ he was...

But he knew that would never happen.

Mark didn't love him.

* * *

Mark rolled onto his back and sighed, turning the evening over in his head, Jack had looked so pallid and tired. It was as if as soon as he's reached Mark's house, he had changed.

The Alpha couldn't help flinching at the twist his stomach made at that feeling.

Suddenly a soft cry from down the hall caught his attention, the redhead looking up and waiting to see if he was just hearing things.

It happened again, followed by a whimper.

Part of Mark rationalised that Jack was just having a dream, but his instincts were pricking at him, forcing him out of bed leading him to the door of the spare room.

He lifted his hand to knock and caught a scent he didn't recognise...but yet did...

Shaking his head, he knocked quietly on the door.

“Jack? You okay?” His sensitive hearing picked up a soft gasp and a rustle of the bedclothes.

“Uh...yeah...I'm fine!” Jack's voice was breathy but panicked, the Alpha's scent creeping under the door and setting his nerves on fire. “Mmmm...ohh...”

Mark moved closer to the door, the scent of a ripe Omega in heat suddenly hitting his nose. The low growl in his chest was a kneejerk reaction to the smell,and the whine that came from the other side of the door did nothing to ease the rapid hardening of his cock against his boxers.

“Fuck...” The Alpha hissed between gritted teeth, one hand fisted against the door, the other palming himself. “...are you...in heat??”

Jack whined, his clothes now clinging to him with sweat and slick. “Oh god...Mark...you need to stay out there...”

“Jack...I didn't know...” The American sighed, resting his forehead against the door. It made sense now, how Jack was earlier, how pale and tired he had looked. “Why didn't you tell me?”

* * *

The Irishman bit his lip, blinking away tears. He might as well come clean before he was unable to think clearly.

“I didn't...want it to...ngh...change how you felt...about me...”

There was a silence from behind the door, Jack's heart hammering in his chest as he waited for a response, his stomach twisting in a mixture of nerves and his heat.

“Jack...I love you...” Mark's soft deep voice said quietly. “Fuck, I'm _in_ love with you. I loved you when I thought you were a beta, and I love you now. I love you for  _you_...not your sub gender."

The Omega let out a choked gasp at his best friend's words. Slowly, he mustered enough energy to pull himself from the bed to stand closer to the door.

“You...you love me?”

 


	3. Chapter 3

**Notes for the Chapter:**

> Welp, here is part of the smuts! I was going to put it all into one chapter, but as you'll see, I think it will be better split in two :)
> 
> A huge thank you to everyone who has provided feedback, it really does make my day xx

Mark huffed out a laugh, placing a hand on the door, as if he could feel the Omega on the other side.

“How could I _not_ love you? You're smart, funny, kind, gorgeous...” The Alpha fisted the other hand in his hair, tugging at the dyed strands. “Look...the point is, I loved you before I knew what you were.” Sighing again, he pushed away from the door. “I'm not going to do anything you don't want to, but if you need me to bring you anything...”

The door unlocked and streak of green launched at him, automatically reaching out to catch the Omega as arms and legs wrapped around his shoulders and waist. Jack's fingers pressed in the short dark hair at the back of the Alpha's head as he buried his face in Mark's neck.

“Oh god...I...thought...” Jack raised his head and it hurt Mark's heart to see there were tears in those beautiful blue eyes. “I didn't...” A large warm hand cupped his cheek, brushing away his tears. “I love you too.”

A low rumble sounded in the Alpha's chest at Jack's words, Mark's fingers pulling him closer, drawing the Omega into a kiss. Jack whimpered, wrapping himself tighter around the other man.

“Mark...please...” The Alpha groaned at the fingers in his hair tightening, the warm dampness from Jack now soaking into his boxers as the Omega pressed himself up against him.

The American growled, stumbling forward into the room and kicking the door shut. He gently laid Jack on the bed, placing a kiss on the full swollen lips.

“Jack...are you sure about this? I...” The American stopped as a pale hand reached up and brushed his hair out of his face, fingers moving down to trailalong his jaw.

“I want this. I want _you_...” The Omega inhaled and bit his lip, his flushed cheeks turning darker. “The t'ought of this, of us...has...gotten me through my heats in t'past...”

Mark let out a loud groan at this admission, images of Jack fucking himself on his fingers and thinking of him flashing across his mind. “Fuck...Jack...”

Christ, he was so hard it _hurt_.

The Alpha moved to kiss the Irishman again, trailing his lips down the pale throat and chest before hooking his fingers into the waist band of Jack's pyjama bottoms and pulling them down as he pressed kisses to the trail of hair from his navel down to his groin.

Jack arched up as the cool air hit his damp skin, whining as he twisted his hands in the sheets. A deep low growl sounded in Mark's chest as Jack's scent hit him tenfold, a fresh wave of slick trickling down the Omega's trembling thighs.

Jack gasped as the Alpha's warm tongue ran slong the inside of his thigh, cleaning the slick from his skin. “God, you taste so good...” The green haired man bit his lip as Mark nipped the crease in his thigh, the redhead's fingers finding the Omega's hole. “Don't worry baby, I'm going to take care of you.”

“Maaark...”

“Shh...it's okay...” Mark looked up at the beautiful man underneath him, eyes glazed and pupils wide with lust as he looked back. “I want to make sure you can take my knot...”

Jack had never been knotted before and from what he had seen, Mark was generously endowed. He nodded, squeaking as the Alpha nipped his thigh again before flashing a gorgeous smile and sliding his finger in further. The Omega's fingers tightened in the sheets, ever nerve alight at the finger slowly pushing inside.

The Alpha carefully watched for any sign of distress or discomfort before adding another finger, the rumbling purr in his chest soothing the Omega, who responded with another small whine.

“You're doing so well baby...” Mark murmured, his voice low and rough, sweat beading at his forehead. “I'm going to add a third finger, it may hurt slightly but I want you to relax and breathe...”

The green haired Omega nodded, face contorting at the sensation but keeping his breathing stready. He felt the fingers gently stretch him, his muscles already pliant with the heat hormones and the slick making it easy for Mark's movements.

Suddenly, one of the fingers grazed against his prostate, sending a jolt of electricity up his spine, a broken cry ripping from his throat. The Alpha chucked, pressing a kiss to the Omega's thigh.

“Feel good?”

“Fuck...” His hips flew off the bed as Mark did it again. “Fuck! Mark, please...” Without another word, the Alpha carefully withdrew his fingers and sat back, his eyes never leaving the panting, shuddering Omega as he licked the slick from them.

“Mmmm, I could get used to the taste of that...”

“Pleeeeease...Alpha, please...” Jack whined, arching and writhing, his body was aching with the heat and Mark's fingers had only dampened the sensation slightly, the burn rising again once he had withdrawn.

He heard a rustle of fabric before Mark covered his body with his own, the Omega reaching up to press as much of himself to the Alpha's toned, tanned body, his head swimming in the spicy, warm scent as lips sought out his.

Mark wrapped one arm around Jack's hips, lifting them slightly whilst the other guided his erection into the other man's warm, willing body.

A sharp gasp sounded from the Omega, turning into a loud, broken whine as he was filled, his body screaming in relief, crying out for the Alpha to knot him, breed him, posess him...

“Mine...” Mark bit out behind clenched teeth, a low deep growl in his chest as he was surrounded by soft, wet, heat. One of Jack's hands gripped his hair, the other was cluching at the Alpha's shoulder, blunt nails scratching the tanned skin.

The Omega gasped as the Alpha lowered his head to the pale column of his throat, the drag of hot, hard flesh inside him sending his nerves singing as the warm mouth nipped and licked along his neck. Squeezing his eyes shut, he wrapped himself tighter around the other man, head thrown back against the pillow.

“Alpha...”

“That's right...” Mark's thrusts were deep, lips moving up to the stubbled jaw, teeth grazing the fluttering pulse. “Alpha... _your_ Alpha...”

Jack whined, biting his lip. Arching upwards, he exposed his throat further.

“Mate me...please...Mark...”

 


	4. Chapter 4

Mark lifted his head from Jack's neck. Dark brown eyes stared down into wide blue ones, searching for a sign that the younger man said what he thought he had.

“What did you say?”

“I said I want you t'mate me.”

“Are you sure?

“I love you, I want us t' be together always.” Jack caressed the short black hair at the back of Mark's neck, relishing the low rumble in the Alpha's chest as he moved one hand down to feel it under his fingers.

“I love you too...” Mark said, searching the wide blue gaze. “But are you sure? If we do this, then we do it for life...” Leaning down, the Alpha pressed his lips to the exposed throat before moving back to look at the younger man. “I don't want any other Omega, I just want you. But I want you to be certain...that it's not just the heat talking.”

Jack wrapped his legs around the narrow hips, drawing the Alpha deeper into him, fingers pushing the red hair plastered against Mark's forehead back out of his face, leaning forward to press a kiss to his lips.

“D'you know how many times I've dreamt about us? About you being t'last thing I see at night and t'first thing see when I wake up?” Gentle lips brushed against the tanned handsome face. “How many times I've dreamt carrying our babies, imagining what they would look like? Even though I swore to myself I would never succumb my Omega instinct?” Mark shivered at the thoughts Jack's words conjured behind his eyes. “I've thought about this a lot and there is no other man I would want to spend the rest of my life with.”

“God Jack...” Mark's eyes rolled as Jack's fingers gripped tighter in his hair, the Alpha pressing his teeth against the Omega's neck with a soft growl, satisfied at the answering whine as Jack's grip lessened. “You don't know how long I've wanted to do this...”

The Omega squeaked as the Alpha sat up and pulled him into his lap, arms flying up around the Alpha's shoulders. As Mark jerked his hips upwards, Jack cried out at the angle, a new wave of slick surrounding the Alpha's cock. Sharing a kiss, the two let their instincts take over, their combined scent hanging thick in the air and the feel of each other's bodies almost too much for them to bear.

The Omega clung on as the Alpha set a brutal pace, leaning back on the bed with one arm to help him move deeper.

“Oh...fuck...Alpha...now...please...” Jack bit out between thrusts, body screaming for more. A loud gasp found it's way from his lips as Mark's fingers found his hair, pulling his head back to expose his neck.

The red-headed Alpha ran his mouth up the side of the Omega's throat, relishing the rapid pulse under his lips, the pale skin sweet under his tongue. Moving to the crook of Jack's neck where his scent gland was located, the taste changed slightly, honeyed – almost ambrosial.

Jack cried out as he felt Mark's teeth sink into his neck, his whole body stiffening at the sensation, orgasm catching him by surprise as he came untouched between them, painting their stomachs with his release.

The Alpha groaned at the feel of the Omega's body tightening around him, a low rumble in his chest as he held the younger man as he rode out his orgasm.

“Oh god...I...didn't...” Mark chuckled and pressed a kiss to the Omega's cheek.

“You're in heat baby, I bet I could get you off with just my tongue you’re so hot for it…but maybe another time.” His lips pulled into a feral grin as he started to move again, running his tongue along the bite mark as he thrust upwards into the younger man.

“Ngh! Ah...ah...”

Little whimpers escaped the Omega's lips, punctuating each thrust of the Alpha's hips, the redhead responding with low purr in his chest. Moving his mouth away, Mark tilted his head back as Jack wrapped his arms around the broad shoulders, burying his head in the other man's neck and breathing in.

The Alpha's tanned flesh was warm under his lips, spiced and musky as he darted his tongue out to taste. Scratching his fingers gently through the black and red hair, he bit into the Alpha's shoulder, gasping as the older man's grip on him tightened.

Mark hissed, electricity running through his veins as he felt the dull sting of Jack's bite into his scent gland. The Omega whined against his shoulder, gripping onto him as they both felt the first few strands of their bond start to form and solidify.

“Gonna...knot you...gonna...breed you...” Mark growled, skin on fire with Jack's touch, the bond growing stronger with every touch, every taste, every push and drag of flesh. “You want that baby? You want me to knot you? Fill you up with my cum?”

“Mmm...oh god...yes!” Jack groaned as Mark leant forward to suck bruises on the unmarked side of his mate's neck.

“Everyone is going to know who you belong to...” Easing Jack off his lap, Mark turned the younger man onto his stomach, the Omega immediately shifting, arching his back and lifting his lips. The Alpha bit his lip with a grin, running a hand along one pale thigh before reaching the globes of the Irishman's ass, squeezing as he ran his thumbs along the dripping hole between them.

“Alpha! Now, please!”

Gripping the narrow hips, Mark thrust back into the tight wet heat of Jack's body, the green haired Omega wailing at the depth the Alpha was now able to achieve, his ability to catch Jack's prostate. The redhead curled against his back, pressing him into the bed with each snap of his hips, tongue running along the shell of his ear. “Fuck, gonna take...good care of you...gonna keep...you plugged up with my cum...” Jack groaned, reaching one arm around to grip the back of the Alpha's head as Mark pressed kisses to his shoulder, to his mating bite.

“Alpha...god...you feel so good...” A deep chuckled brushed against his skin as the Omega was caught between the sheets rubbing against his aching erection and the hot, hard Alpha cock inside him. “Gonna...cum...again...” He was aware that the knot at the base of Mark's prick was starting to swell, just starting to catch the rim of his hole with each thrust.

“I'm close too baby...” The younger man felt large strong hands grip his wrists and pin them to the pillow beside his head, the Alpha using his body weight to thrust in deeper, the drag of the expanding knot against Jack's sensitive hole was too much. The Omega was soon cumming again against the sheets with a whimper, Mark's hips stuttering as his knot restricted his movements, pressing the younger man into the bed before shooting his own release with a low growl against the Omega's neck.

Jack moaned at the warmth filling him, Mark's still hard cock twitching inside his body, the Alpha's knot locking them together.

The redhead's breath was heavy against his shoulder as his wrists were released, hands moving around his waist to manoeuvre them onto their sides. Jack let out a breath as his mate settled him against the broad warm chest behind him, wincing slightly as the movement caused the Alpha's knot to scrape against his sensitive insides.

“Sorry.”

“It's okay...” Jack murmured, leaning his head against the other man's shoulder, Mark smiling back at him as the Omega stifled a yawn. The red-headed Alpha ran a possessive hand over the pale hip as Jack turned to kiss his bearded cheek.

“I'll be able to move in about fifteen minutes, then you can nap whilst I sort some things out.”

“Thank you...” Mark chuckled and pressed a kiss to the green hair.

“Hey, I'm an Alpha...I'm programmed to think of these thi-ngh!” Mark was cut short as another orgasm was drawn from him, his body tensing as Jack gasped at the fresh wave of warmth spreading inside him, his cock twitching against his thigh.

Mark blew out the breath he’d been holding as his release subsided, Jack feeling his slowing heartbeat against his back. In the silence of the room, Jack found his heat-addled, sleep deprived mind start to wander, mainly on what would happen once his heat was over and he had to return to Ireland.

His heart hurt at the thought being parted with his Alpha, and the way Mark was pressed against him, holding him so close…his mate felt the same way.

“Hey...” Jack closed his eyes as the redhead pressed his his nose against the green hair. “Silence means you're thinking too much...You're thinking about after this, aren't you?” Jack nodded, Mark sighing against his shoulder.

“I'm just...I mean...what's going to happen after these two weeks?” Jack sighed, leaning his head back against the Alpha's chest, tanned arms wrapping around his waist, pulling him tight against the broad warm body behind him.

“Jack, you are everything to me...if I have to move to Ireland to be with you, I will. If you want to move to LA with me, that's fine too...I just want you to be happy...”

Mark's lips pulled into a lopsided grin as the Omega tilted his head up to nose at the Alpha's jaw.

“You'd do that for me?”

“You're my Omega, my mate...I will do everything in my power to make you happy.” Jack bit his lip, a lump in his throat at his best friend's declaration and a wide smile on his lips.

“You already do.”

 

**Notes for the Chapter:**

> I hope you've enjoyed this fic! I'll be doing a short epilogue chapter but never fear, Alpha!Mark and Omega!Jack will return in the future :)


	5. Epilogue

“Hello everybody, my name is Markiplier and welcome to another vlog. The number of asks for regular updates from you guys was just staggering after the first one Jack and I posted together. So a huge thank you to everyone for their congratulations. Your support has just been incredible.”

Jack leant against the door frame, watching through the crack in the door as Mark smiled warmly into the camera, hands together in a gesture of gratitude as the Alpha updated their subscribers to the situation. They had both been amazed by the wave of love and support when they had decided to tell their fans that they were together.

The week of Jack's heat had been a blur. Mark had bred him so thoroughly during the cycles and made sure he ate, drank and slept in between. As his heat had started to come to an end, the Alpha had spent the increasing time between their sessions pampering his mate, running him long hot baths and massaging his sore body.

As he continued to watch his mate talk to the camera, the Omega thought back to the time they had spent laid on the bed, limbs entwined and as they discussed their future. He had curled up against the Alpha, Mark entwining their fingers with one hand and tracing the dip and curve of Jack’s hip with the other, the two of them making plans for when Jack's visit ended. It was decided that Mark would go back with him to Ireland in order to sort everything out before the two would return and have Jack's things shipped over.

Pulling back to the present, Jack watched as his mate signed off on the video, the Alpha pulling the headphones off his head before looking over.

“Hey...” Mark said, reaching a hand out towards him. Moving into the room, Jack took the proffered hand and allowed himself to be pulled onto the Alpha's lap, a smile on his lips as Mark buried his head in the crook of his neck. “Are you okay?”

“Of course.”

“It’s just that I’ve noticed your scent has changed slightly…just wondered if…” Jack took Mark’s hand and placed it on his stomach, watching the other man’s face as he held it there, the warmth of the Alpha’s palm soaking through his t-shirt. “Jack…”

“Mmmm?”

“You're…”

“Yep.” Mark stared down at his hand and then back up at Jack’s face.

“I’m…?” The Omega’s smile widened as his eyes filled with happy tears, nodding as the Alpha’s other hand reached up to cup his face. “I’m going to be a Daddy…”

“You are.”

Mark murmured words of love, pressing kisses to Jack’s face and brushing away the tears falling from his mate’s beautiful blue eyes. Moving Jack to stand between his legs, the red headed Alpha leant forward, pressing his lips to the flat stomach before wrapping his arms around the Omega’s narrow waist, Jack’s fingers carding through his hair.

"I love you…so much…both of you.”

 


End file.
